As a valve opening and closing timing control apparatus having the configuration described above, JP 2012-189050A (Reference 1) discloses a technology of a speed reduction mechanism in which a ring gear (a second internal toothed gear in Reference 1) is disposed coaxially with a rotation axis (a rotation axis line in Reference 1) and an inner gear (a second planetary gear in Reference 1) is disposed coaxially with an eccentric axis (an eccentric axis line in Reference 1), which has a posture parallel to the rotation axis, such that a portion of an external toothed portion of the inner gear is engaged with a portion of an internal toothed portion of the ring gear, and a drive shaft (a planetary carrier in Reference 1) is fitted into the inner gear.
In this technology, a biasing member (an elastic member in Reference 1), which applies a biasing force required for the engagement of the external toothed portion of the inner gear and the internal toothed portion of the ring gear, is disposed so as to be fitted on the outer periphery of the drive shaft. In addition, in this technology, there is provided a configuration in which components similar to the ring gear and the inner gear described above (a gear member and a first planetary gear in Reference 1) are coaxially disposed to enable two-stage speed reduction, and a pair of inner gears, which is disposed to overlap each other, is connected to each other via a rod-shaped connection member.
In the configuration described in Reference 1, a relative positional relationship between the ring gear and the inner gear in the engagement direction thereof is set by a biasing force of a biasing mechanism, and a relative positional relationship between the ring gear and the inner gear in the direction orthogonal to the biasing direction is set by the connection member.
Considering the engagement between the internal toothed portion of the ring gear and the external toothed portion of the inner gear, when there is a gap (a gap in the direction orthogonal to the biasing direction) between toothed surfaces, abnormal noise may be generated when the toothed surfaces come into contact with each other.
This problem may be solved by providing the rod-shaped connection member described in Reference 1 to regulate displacement of the inner gear in the direction orthogonal to the biasing direction. However, in the configuration in which the displacement of the inner gear is regulated by the connection member, the accuracy of the connection member is required and there is still room for improvement.
In particular, when a speed reduction mechanism is formed of a single ring gear and a single inner gear, a component having the same function as the connection member is especially required, which then causes an increase in the number of components.
Thus, a need exists for a valve opening and closing timing control apparatus which is not susceptible to the drawback mentioned above.